Functionally gradient SiC/SiC ceramic matrix composites with tailored properties for turbine engine applications

Abstract

A ceramic matrix composite with a ceramic matrix and a gradient layering of coating on ceramic fibers. The coating typically improves the performance of the composite in one direction while degrading it in another direction. For a SiC-SiC ceramic matrix composite, a BN coating is layered in a gradient fashion or in a step-wise fashion in different regions of the article comprising the ceramic. The BN coating thickness is applied over the ceramic fibers to produce varying desired physical properties by varying the coating thickness within differing regions of the composite, thereby tailoring the strength of the composite in the different regions. The coating may be applied as a single layer as a multi-layer coating to enhance the performance of the coating as the ceramic matrix is formed or infiltrated from precursor materials into a preform of the ceramic fibers.

1. A method of manufacturing a ceramic fiber preform for use in a ceramic matrix composite, the method comprising:
 providing a fiber preform having a plurality of ceramic fibers; 
 defining a plurality of regions of the fiber preform on the basis of variations in the desired level of resistance to in-plane stress and variations in the desired level of resistance to interlaminar stress among corresponding regions of the ceramic matrix composite, the plurality of regions including a first region and a second region; 
 applying BN to the first region, yielding a first BN layer having a thickness in the range of about 0.3 micron to about 1.0 micron; 
 applying BN to the second region, yielding a second BN layer having a thickness of less than or equal to about 0.3 micron; 
 applying Si-doped BN to the first BN layer, yielding a first Si-doped BN layer having a thickness in the range of about 0.4 micron to about 0.6 micron; 
 applying Si-doped BN to the second BN layer, yielding a second Si-doped BN layer having a thickness of less than or equal to about 0.3 micron; 
 applying SiN to the first Si-doped BN layer, yielding a first SiN layer having a thickness in the range of about 0.75 micron to about 1.25 micron, thereby forming a first multilayer fiber coating corresponding to the first region; and 
 applying SiN to the second Si-doped BN layer, yielding a second SiN layer having a thickness of about 0.5 micron, thereby forming a second multilayer fiber coating corresponding to the second region. 
 
     
     
       2. The method of  claim 1 , wherein the ceramic fiber is selected from the group consisting of SiC, Al 2 O 3  and Si—N—C. 
     
     
       3. The method of  claim 1 , wherein the thickness of the first BN layer is about 0.3 micron. 
     
     
       4. The method of  claim 1 , wherein the thickness of the second BN layer is about 0.3 micron. 
     
     
       5. The method of  claim 1 , wherein the thickness of the second Si-doped BN layer is about 0.3 micron. 
     
     
       6. The method of  claim 1 , further including applying carbon to the first SiN layer, yielding a carbon layer having a thickness of less than or equal to about 0.1 micron. 
     
     
       7. The method of  claim 1 , further including applying carbon to the first SiN layer, yielding a carbon layer having a thickness of about 0.05 micron. 
     
     
       8. The method of  claim 1 , wherein the plurality of regions includes a third region, and further including applying BN to the third region, yielding a BN monolayer having a thickness of about 1.0 micron. 
     
     
       9. The method of  claim 1 , wherein the plurality of ceramic fibers essentially includes only ceramic fibers having a diameter in the range of about 5 microns to about 20 microns. 
     
     
       10. The method of  claim 1 , wherein the plurality of ceramic fibers essentially includes only ceramic fibers having a diameter in the range of about 10 microns to about 15 microns. 
     
     
       11. The method of  claim 10 , wherein the plurality of ceramic fibers consists essentially of ceramic fibers composed of SiC. 
     
     
       12. The method of  claim 1 , wherein the first region and the second region are contiguous. 
     
     
       13. The method of  claim 12 , wherein a gradient is defined by the first multilayer fiber coating and the second multilayer fiber coating. 
     
     
       14. The method of  claim 1 , wherein the first region and the second region are not contiguous.